When it comes to what freaks American adults out, snakes rank right up there with heights, public speaking, and bugs. They can carry lethal venom in their bites and be strong enough to strangle and eat alligators. Still, snakes are an important part of the ecosystem as a whole because they help control pest populations and help maintain the planet’s biodiversity.
They can also probably hear all of the bad things humans are saying about them. In a study published February 14 in the journal PLOS One found that snakes can hear and react to sounds in the air in addition to feeling vibrations in the ground.
[Related: Scientists just found out female snakes have two clitorises.]
A team at the University of Queensland (UQ) in Australia played three different sound frequencies–two that were airborne and one that was a ground vibration– to captive-bred snakes one at a time in a soundproof room and observed their reactions. They used 19 snakes that represented five genetic families of reptiles.
“Because snakes don’t have external ears, people typically think they’re deaf and can only feel vibrations through the ground and into their bodies,” said study co-author Christina Zdenek, a biologist from UQ’s School of Biological Sciences, in a statement. “But our research – the first of its kind using non-anesthetized, freely moving snakes – found they do react to sound waves traveling through the air, and possibly human voices.”
By testing both vibrations and airborne sounds, they were able to test two types of hearing in snakes. The tactile hearing that occurs in the snake’s belly scales and the airborne hearing that occurs in the snakes’ internal ear.
According to the study, the reaction strongly related to the genus of the snakes.
“Only the woma python tended to move toward sound, while taipans, brown snakes, and especially death adders were all more likely to move away from it,” Zdenek said. “The types of behavioral reactions also differed, with taipans in particular more likely to exhibit defensive and cautious responses to sound.
These different reactions are likely due to evolutionary pressures over millions of years that were designed to help snakes survive and reproduce.
[Related: After the dinosaurs, Earth became an all-you-can-eat buffet for snakes.]
“For example, woma pythons are large nocturnal snakes with fewer predators than smaller species and probably don’t need to be as cautious, so they tended to approach sound,” Zdenek said. “But taipans may have to worry about raptor predators and they also actively pursue their prey, so their senses seem to be much more sensitive.”
The findings challenge the assumption that snakes can’t hear sounds like yelling or humans talking and may reshape beliefs and ideas on how they react to sounds. Since snakes are generally timid and hide much of the time, it has been harder to study them.
“We know very little about how most snake species navigate situations and landscapes around the world,” Zdenek said. “But our study shows that sound may be an important part of their sensory repertoire.